Wire Electrochemical Machining With High-Speed Electrolyte Flushing Of Thick Structures

Low-cost and high efficiency machining for thick workpieces presents a bottleneck when fabricating parts with ruled surfaces like the fir-tree slots in a turbine disc and square slit torsion spring.These parts are usually made of difficult-to-cut materials,and no recast layer or micro crack is allowed on the machined surface.Wire electrochemical machining(WECM)is very suitable for the machining needs of such parts.In this paper,aiming at the problem that it is difficult to discharge the electrolytic products in the machining gap when the workpiece with large thickness is processed by WECM,the experimental research on high-speed flushing WECM of thick structures was carried out.Characterized by a relatively short flow path,a pulsating radial electrolyte supply in WECM was proposed to reduce the accumulation of electrolytic products and improve machining accuracy,machining efficiency and machining capacity of large thickness workpiece.The following work has been accomplished:(1)A pulsating radial electrolyte supply in WECM is proposed.In this method,a tube electrode with an array hole on the side is used as the tool cathode.The electrolyte enters from the two ends of the tube electrode,and flows out of the liquid hole of the array on the side at high speed into the machining gap.The workpiece is cut by the principle of electrochemical machining.The flow distribution of tubular electrode with uniform aperture was analyzed.it was found that the flow rate of the electrolyte from the outlet holes on both sides is less than the middle part,resulting in insufficient liquid supply on both sides and affecting the processing stability.A flow field model of machining gap was established and the influence of the shape of the inlet section at both ends,the spacing of the holes in the side array and the diameter distribution on the flow distribution in the direction of the workpiece thickness was investigated.The results show that the consistency of electrolyte flow rate of a tube electrode with holes of varying diameters is significantly improved.(2)The experiment of electrochemical drilling on a tube electrode with varying diameters was carried out.The effects of pulse duty ratio and pulse frequency on the machining diameter and surface are investigated.And the quantitative relationship and parameter selection pattern among the feed rate,the applied voltage,and the diameter of the outlet holes were fitted experimentally.A tube electrode with holes of single diameter of 0.2mm and a tube electrode with holes of optimized diameter distribution were prepared.They had a hole number of 30 and a hole spacing of 1mm.(3)The experimental research on a pulsating radial electrolyte supply in WECM was carried out.Using a tube electrode with holes of varying diameters as a tool electrode,kerfs were machined at a feed rate of 6?m/s in a 30 mm-thick stainless steel block steadily.It is verified that the ability of cutting large thickness workpiece can be effectively improved by using a tube electrode with holes of varying diameters.The spray angle of the outlet hole of the tool electrode was optimized.The comparison experiments between WECM with axial electrolyte flushing and a pulsating radial electrolyte supply in WECM were carried out.The results show that,20 mm thick workpiece could be machined using WECM with axial electrolyte flushing,while 30 mm thick workpiece could be machined using a pulsating radial electrolyte supply in WECM.The maximum feed rate that could be achieved by using a pulsating radial electrolyte supply in WECM was higher than that of WECM with axial electrolyte flushing.The width of kerfs was tapered along the depth of the workpiece using WECM with axial electrolyte flushing.(4)The experiment of machining a square slit torsion spring using WECM with axial electrolyte flushing was carried out.It adopts the compound movement mode of ultra-low speed rotation and low speed linear feed to machine.The fixtures were improved,the effect of voltage on feed rate was studied,and the processing route was optimized.A square slit torsion spring with a cutting thickness of 6.5mm,an average slit width of 1.006 mm,and a cutting length of more than 1m was prepared.